This invention relates to a control valve, including a pressure control valve to be employed for refrigerator and air conditioner, an evaporation temperature control valve and etc. A control valve of the prior art, for example a pressure control valve, consisting of a valve proper, an inlet coupling and an outlet coupling, employs some means, such as O rings or welding, for keeping parts such as valve means under the airtight position. Further, control means is exposed to outside. Therefore, many kinds of parts are necessary, causing a failure requiring many steps in assembly. Further, since there are many parameters causing unsatisfactory airtight position, observed is a tendency to be readily influenced by the ambient pressure.